US Democratic presidential candidate Hillary Clinton has said she regretted saying "half" of Republican rival Donald Trump's supporters belonged in a "basket of deplorables".

Clinton, however, argued on Saturday that the word "deplorable" was reasonable to describe much of Trump's campaign.

"Last night I was 'grossly generalistic', and that's never a good idea. I regret saying 'half' - that was wrong," Clinton said in a statement, less than 24 hours after she made the comments at a fundraiser in New York.

But "Trump has built his campaign largely on prejudice and paranoia," she said, adding: "I won't stop calling out bigotry and racist rhetoric in this campaign."

On Friday, Clinton, who has said she is the candidate to unify a divided country, said Trump's supporters were "racist, sexist, homophobic, xenophobic, Islamophobic".

READ MORE - Hillary Clinton and Donald Trump: Candidates-in-Chief

Trump and his supporters quickly reacted.

"Wow, Hillary Clinton was SO INSULTING to my supporters, millions of amazing, hard-working people. I think it will cost her at the polls!" Trump said in a tweet.

Twitter user Basketeer Vendetta, under the account Vendetta92429, tweeted a photo of Trump supporters wearing campaign T-shirts and hats, adding: "Proud to be part of the #BasketOfDeplorables with my fellow Americans."

But some Twitter users agreed with Clinton, referencing remarks by Trump that have been called racist, such as when he described some Mexican immigrants as drug dealers and rapists.

READ MORE: Can Hillary Clinton change gender roles in politics?

Clinton spokesman Nick Merrill said in a series of tweets after the remarks that Clinton has been talking about the "alternative right", or "alt-right" movement, which often is associated with efforts on the far right to preserve "white identity", oppose multiculturalism and defend "Western values".

Merrill argued that "alt-right" leaders are supporting Trump and "their supporters appear to make up half his crowd when you observe the tone of his events".

Clinton has made similar comments in the past. In an interview with Israeli TV this week, Clinton said that Trump supporters are "what I call the deplorables; you know, the racists and the, you know, the haters, and the people who are drawn because they think somehow he's going to restore an America that no longer exists".

The rhetorical scuffle comes as the candidates head into the final two months of the campaign, with Trump trying to make up ground on Clinton before the November 8 election.

Source: Agencies